That works for tissues that can be temporally removed and returned at a later date like a sample of bone marrow.

However, such an approach is impossible for organs like the liver, heart or brain. It is why doctors have attempted the gene editing inside the patient’s body.

The trial is testing only the safety of performing the gene editing and it will require more research to know if it could be a valid therapy.

So far there have been no side effects in Mr Madeux and if everything continues to go well, then up to nine patients will receive the experimental procedure as part of the study.

‘New frontier’

Dr Sandy Macrae, from Sangamo Therapeutics, which designed the therapy, said: “For the first time, a patient has received a therapy intended to precisely edit the DNA of cells directly inside the body.

“We are at the start of a new frontier of genomic medicine.”

Further safety trials using the same technology to treat haemophilia B and Hurler syndrome are also planned.

Mr Madeux says he is prepared to have his DNA altered “if it will prolong my life and help scientists find cures for humankind”.